Bug 938046 - Part 1. Iterate through variable not over const.  r=dkeeler
Bug 938046 - Part 2. Get issuer uses getchain to comput issuer.  r=dkeeler
 Bug 938046 - Part 3. Iterate only through valid users on getchain  r=dkeeler
Bug 938046 - Part 4. Tests for consistency of getchain and getissuer. r=dkeeler